Amphion was the personal pleasure craft of king Gustav III of Sweden. She was designed by Fredrik Henrik af Chapman, built at Djurgårdsvarvet in Stockholm in the summer of 1778, and launched the same year. Amphion, named after Zeus' son and culture patron in Greek mythology, served as a royal yacht and headquarters ship. The ship was essentially a modified turuma, a type of shallow-draught frigate that served in the Swedish archipelago fleet. She was equipped with oars to allow her maneuverability of a galley while retaining a broadside of heavy guns and a full rig. She was equivalent to similar "archipelago frigates" of the archipelago fleet, but at Gustav III's request, she was built without heavy cannons and therefore differed significantly from the other ships of the same type.